Frog-eye leaf spot, SDS showing up in Tennessee soybean fields

This summer’s unusually cool, wet conditions have been nearly ideal for the corn and soybean crops, but they’ve also been favorable for soybean diseases such as frogeye leaf spot and SDS or sudden death syndrome.

Heather Young-Kelly, Extension plant pathologist with the University of Tennessee, talked about those diseases at the Asgrow/DeKalb agAcademy in Union City. Dr. Kelly was one of several university and Extension speakers who participated in the annual event.

“This season in soybeans in Tennessee we are getting reports of frogeye leaf spot in the field in susceptible varieties,” she said. “In my own research plots, I’m seeing it where I expect it. I have seen that it’s a little delayed in its development due to the low relative humidity we’ve been having and some of the cooler temperatures.”

The cooler temperatures and the rains are the right conditions for SDS or sudden death syndrome. “We are starting to get reports of it in Tennessee,” she said. “That is a fungus that infects through the roots, and the foliar symptoms you see, yellowing between the veins and possibly necrosis and browning between the veins. That’s actually due to the toxin that fungus creates within the plant after it’s been infected through the roots.”

She said variety selection is important for it and for other diseases to better moderate and manage them.

Stem canker is a disease that looks similar to SDS, but stem canker is more prevalent in hot dry years, which 2014 has not been until recent days when clearer skies and warmer temperatures began to move into the region.

“There’s a very low probability we will see any of it (stem canker) this year,” she noted.